This invention relates to a motorized power steering control device, and more particularly to a motorized power steering control device which is adapted to be fed with power assisting force by driving of an electrical motor.
A conventional motorized power steering control device is generally constructed in such a manner as shown in FIG. 3. More particularly, the conventional motorized power steering control device includes a controller C for controlling an electric motor m, which controller C is connected through a drive wiring 9 to a battery B for driving the electric motor m. The battery B has an alternator 13 connected thereto. The alternator 13 is connected to an engine (not shown), resulting in acting as an AC generator adapted to operate depending on rotation of the engine and exhibit a rectifying function.
The drive wiring 9 has a wiring 11 for the controller C branched therefrom, which wiring 11 is connected through an ignition switch IC to a power circuit 10 arranged in the controller C. The power circuit 10 has a backup wiring 12 connected directly thereto without interposing the ignition switch IG between the power circuit 10 and the backup wiring 12.
The power circuit 10 constructed as described above acts to apply a main voltage to a computer control circuit 2 when the ignition switch IC is turned on and apply a backup voltage thereto when it is turned off. The backup voltage permits a backup current of a required level to be fed to the controller C, to thereby permit storage in the controller C to be kept, even when the ignition switch IG is turned off.
The conventional motorized power steering control device also includes a torque sensor 3, a vehicle velocity sensor 4 and an engine speed sensor 5 each connected to the controller C so as to act as a travel condition detection means.
The controller C generally includes a drive circuit 1 for controlling a voltage applied to the electric motor m and the control circuit 2 for controlling the drive circuit 1.
The above-described drive wiring 9 is connected to the drive circuit 1 of the controller C, to thereby permit the electric motor m to be connected to the drive circuit 1 therethrough. The control circuit 2 for controlling the drive circuit 1 is connected to the power circuit 10.
The torque sensor 3, vehicle velocity sensor 4 and engine speed sensor 5 are connected through interfaces 6, 7 and 8 arranged in the controller C to the control circuit 2, respectively.
The torque sensor 3 is arranged so as to detect steering torque inputted to a handle of a vehicle and the vehicle velocity sensor 4 acts to detect a velocity or speed of the vehicle. The control circuit 2 actuates the drive circuit 2 depending on the steering torque and vehicle velocity thus detected by the torque sensor 3 and vehicle velocity sensor 4, so that the drive circuit 1 varies a voltage applied to the electric motor m.
Also, the engine speed sensor 5 detects an engine speed of the vehicle. More specifically, for example, the engine speed sensor 5 may be constructed so as to actuate the power circuit 10 when an engine speed is not increased or an engine is not driven irrespective of turning-on of the ignition switch IG. This permits a backup voltage to be applied to the control circuit 2, resulting in the motorized power steering control device being kept from exhibiting its control function and consumption of power stored in the battery B being restrained to prevent full discharge of the battery B.
In the conventional motorized power steering control device constructed as described above, the battery B is used as a power supply for driving the electric motor m, as well as a power supply for the controller C. Also, the conventional motorized power steering control device is constructed so as to permit on-off operation of the controller C to be carried out in association with the ignition switch IG for driving the engine, so that starting of the engine leads to application of a main voltage to the control circuit 2. This results in the motorized power steering control device exhibiting its control function.
Such on-off operation of the controller C in association with the ignition switch IG requires that the controller wiring 11 comprises an external wiring. Unfortunately, this leads to an increase in manufacturing cost of the motorized power steering control device and requires a significant space for mounting of the motorized power steering control device in a vehicle.
Further, the control circuit 2 of the controller C, as described above, has the three sensors or the torque sensor 3, vehicle velocity sensor 4 and engine speed sensor 3 connected thereto so as to act as the travel condition detecting means. Such construction requires arrangement of wirings for the three sensors, interfaces therefor and the like, leading to a further increase in manufacturing cost of the device and complication in structure thereof.